This invention relates to optical fibres and in particular sheathed optical fibres.
A method of installing optical fibre transmission lines is disclosed in European patent application No. 83306636.8 (Title: Optical Fibre Transmission Lines, Applicants: British Telecommunications, Inventors: M. H. Reeve and S. A. Cassidy and corresponding to U.S. Pat. No. 4,691,896), which utilizes the drag forces generated by gas flow to propel optical fibre transmission lines through tubular installation pathways, for insertion or withdrawal of such lines. The optical fibre transmission lines usually comprise optical fibre members in which one or more optical fibres are enclosed in a common jacket.